Oxidation resistant iron-chromium alloy



United States Patent 2,994,604 OXIDATION RESISTANT 1RON=CHROMIUM ALLOY James A. McGurty, Cincinnati, and John F. Collins,

Hamilton, Ohio, assignors to General Electric Company, a corporation of New York No Drawing. Filed Sept. 25, 1959, Ser. No. 842,518 3 Claims. (Cl. 75124) This invention relates to high temperature, oxidation resistant alloys and, more particularly, to alloys of iron, chromium, yttrium and palladium with improved workability.

For applications in air, the field of high temperature metallurgy is, for most practical purposes, limited to the utilization of oxidation resistant iron base and nickel base alloys, and the use of even these materials is limited to temperatures not in excess of 2000 F. The only other generally available materials which might be expected to have useful strength, oxidation resistance above 2000 F. and workability are chromium base or ironchromium base alloys. While high temperature, high strength, structural, chromium base and iron-chromium base alloys do exist, the usefulness of such alloys has been limited by oxide film formation on the surface of such alloys which does not afford suflicient protection against further oxidation at high temperatures. The chromium oxide film which is formed during heating of the metal in air provides some useful protection at temperatures up to 2000 F. Above this temperature, oxidation is sufficiently rapid to discourage use of the metal at such elevated temperatures.

In copending application, Serial No. 842,517, filed September 25, 1959, in the names of James A. McGuIty and John F. Collins, a ternary oxidation resistant ironchromium alloy is disclosed and claimed which consists of from 0.5 to 5.0 weight percent yttrium, from 20.0 to 95.0 weight percent chromium, and the balance being iron. Iron-chromium base alloys with small amounts of yttrium are stable in air to temperatures well above 2000 F. These ternary alloys of iron, chromium and yttrium have good oxidation resistance at temperatures in excess of 2000 F.

Iron-chromium base alloys which would provide high strength, good oxidation resistance, and cladding protection for base alloys at temperatures in excess of 2000 F. are desirable. The invention of the present application provides such iron-chromium base alloys with improved workability.

It is an object of our invention to provide an alloy of iron, chromium, yttrium and palladium.

It is another object of our invention to provide an ironchromium base alloy with improved workability.

It is another object of our invention to provide an alloy which has superior oxidation resistance at temperatures in excess of 2000 F.

It is a further object of our invention to provide an iron-chromium base alloy with oxidation resistance at elevated temperatures which does not affect adversely the workability of the alloy.

In carrying out our invention in one form, from 0.5 to 1.0 weight percent palladium, and from 0.5 to 3.0 weight percent yttrium are combined with an iron-chromium base alloy having from 35.0 to 50.0 weight per- 2,994,604 Patented Aug. 1, 1961 cent chromium and the balance of iron to provide a high temperature oxidation resistant alloy with improved workability.

These and various other objects, features and advantages of the invention will be better understood from the following description.

We discovered unexpectedly that small additions of palladium and yttrium to iron-chromium base alloys produced alloys which had superior oxidation resistance in air at temperatures in excess of 2000 F. and improved workability. The addition of from 0.5 to 1.0 weight percent of palladium, and from 0.5 to 3.0 Weight percent yttrium to iron-chromium alloys having from 35.0 to 50.0 weight percent chromium and the balance of iron provided these extraordinary effects.

During the research which led to the discovery of these oxidation resistant iron-chromium alloys, a series of small vacuum melted iron-chromium-yttrium-palladium ingots were prepared. These ingots containing from 0.5 to 1.0 weight percent palladium, from 0.5 to 3.0 weight percent yttrium, from 35 .0 to 50.0 weight percent chromium and the balance of iron were subsequently hot and cold rolled to sheet stock. The data tabulated in Table I shows the improved workability of iron-chromium-yttrium-palladium alloys as compared with iron-chromium and ironchromium-yttrium alloys.

While other modifications of this invention which may be employed within the scope of the invention have not been described, the invention is intended to include all such as may be embraced within the following claims.

What We claim as new and desire to secure by Letters Patent of the United States is:

1. An alloy of iron, chromium, yttrium and palladium which consists of from 0.5 to 1.0 weight percent palladium, from 0.5 to 3.0 weight percent yttrium, from 35.0 to 50.0 weight percent chromium, and the balance being iron.

2. An alloy of iron, chromium, yttrium and palladium which consists of 1.0 weight percent palladium, 1.0 weight percent yttrium, 45.0 weight percent chromium, and the balance being iron.

3. An alloy of iron, chromium, yttrium and palladium which consists of 1.0 weight percent palladium, 1.0 Weight percent yttrium, 50.0 weight percent chromium, and the balance being iron.

References Cited in the file of this patent UNITED STATES PATENTS 1,167,827 Kaiser Jan. 11, 1916 2,813,789 Glaser Nov. 19, 1957 FOREIGN PATENTS 877,045 France Nov. 25, 1942 

1. AN ALLOY OF IRON, CHROMIUM, YTTRIUM AND PALLADIUM WHICH CONSIST OF FROM 0.5 TO 1.0 WEIGHT PERCENT PALLADIUM, FROM 0.5 TO 3.0 WEIGHT PERCENT YTTRIUM, FROM 35.0 TO 50.0 WEIGHT PERCENT CHROMIUM, AND THE BALANCE BEING IRON. 